In steam driven power plants usually superheated steam is used to run the turbines. In order to avoid damage to the turbine or to overheat the same, it might be important to control the temperature of the supplied steam. The development in this field goes toward higher temperatures of the supplied superheated steam. This increases the demand on the equipment, which also includes the attemperator.
An attemperator is in this context used to lower the temperature of the superheated steam. The attemperator sprays cooling water into the flow of the superheated steam in the supply pipe. When mixing with the steam the water evaporates and thereby takes thermal energy from the steam such that it will be cooled. The water is injected into the steam supply pipe at a section that is provided internally with a lining pipe.
The purpose of the lining pipe section is to protect the steam pipe section from the high temperature of the superheated steam in the region where the water is injected.
Since the temperature of the superheated steam may be very high, such as above 600° C., the temperature difference between the water and the steam will be very high imposing stresses to the steam pipe section.
A representative example of an attemperator is disclosed in U.S. Pat. No. 9,038,993, which describes an attemperator corresponding to the preamble of claim 1 in the present application. Other examples of attemperators are disclosed in U.S. Pat. Nos. 2,421,761, 4,421,069 and CN 102748747.